Continuous conversion and coking of heavy liquid hydrocarbons



Patented May 27, 1952 CONTINUOUS CONVERSION AND COKING OF HEAVY LIQUIDHYDROCARBONS William K. Hunter, Lyons, assignor to versal Oil ProductsCompany, Chicago, Ill., 'a

corporation of Delaware Application January 6, 1950, Serial No' 137,105

Claims.

This invention relates to an improved method for effecting the thermalconversion of heavy residual petroleum stocks in a continuous cokingoperation. More specifically the improved operation provides for thecontinuous conversion of heavyv hydrocarbon charge stocks in a moving orfluidized bed system wherein heated coked particles provide for thethermal conversion of the charge stock, and in addition pro-vides meanswhereby a separately withdrawn stream of hot subdivided particles aidsin the fractionation to obtain desired product streams.

During such periods when there is little or nov demand for heavyresidual fuels, it is advantageous to refiners to process the heavyliquid stocks in a coking operation in a manner to produce more valuablelight oils, which may be used as furnace or diesel fuels, and catalyticcharging stock to in turn produce more gasoline and light heating oils.Excess particulated coke may be withdrawn and utilized to advantage, toprovide for example, valuable metallurgical coke, or alternately it maybe utilized in combination with oil to supply burners for furnaces orthe like with a desirable fuel. A continuous moving bed or iiuidizedcoking operation, such as provided by the present invention, is ofcourse more desirablevthan the earlier methods of coking heavy oils inseparate drums or charnbers, wherein the oil was flash distilled todryness and coke deposited on the inner walls of the chamber, andwherein two or more chambers were necessary to provide a continuousoperation ofthe unit. Also, the'coke deposit built up on the chamberwalls was necessarily removed manually or by mechanical equipment, andthe periodic removal of such coke was both time consuming and expensive.

It is a principal object of the present invention to provide acontinuous conversion and coking' operation for heavy liquid residualhydrocarbons in the presence of heated subdivided particulated material,preferably coke particles, with means for utilizing a separatelywithdrawn stream of hot coke particles to supply7 heat and aid in thefractionation of the resulting product stream of the coking operation.

It is a further object of the present invention tov provide a-separateiiash chamber or contacting zone wherein a separately withdrawn heatedstream of coked particles contacts the heavy residual bottoms of thefractionating zone, which in turn receives the vaporous product streamfrom the coking and conversion zone ofthe unit, whereby to cause adesired flashing and distilling of the bottoms and to supply heat to:the' fractionating zone for producing additional lower boiling petroleumfractions.

It is a still further object of the present invention to provide amethod and meansfor contacting the heavy residual bottoms from thefractionating zone of the unit with hot coke particles in acountercurrent operation within a conned dash zone, whereby a reliuxstream of resulting distillate is supplied to the fractionating zone anda slurry stream of particles with unvaporized bottomsA is provided forrecycling to the contacting and coking zone.

Briefly, the present invention provides an improved process for thethermal conversion of a heavy hydrocarbon charge stream to provide moredesirable components, wherein the charge stream continuously contactsVsubdivided heat carrying particles in a coking and conversion zone,resulting hydrocarbon vapors are withdrawn and passed to a suitablefractionating zone while subdivided particles with a coke depositionthereon are withdrawn and passed to a heating and burning zone, thecoked particles being contacted in the latter zone with a regulatedstream containing air or free oxygen whereby at least a portion of thecoke deposition is burned to provide for the heating' of the particles,resulting flue gases are dischargedY from the upper portion ofthe-burning and heating zone, while at least a portion of the resultingheated subdivided particles are returned to the coking zone to supplyheat and contacting material for eil'ecting the aforesaid conversion andcoking of the charge stream, with ther improvement comprising,fractionally separating the hydrocarbon vapors being passed from thecoking and conversion zone within a confined fractionating zone,continuously withdrawing desired hydrocarbon fractions from the latterzone while passing the resulting unvaporized bottoms from the lowerportion of the fractionating zone to a separate confined flash zone,continuously withdrawing a stream of hot subdivided particles from atleast one ofthe aforementioned particle contacting Zones and passingthem to the confined flashing zone, contacting the fractionating bottomsstream in the latter zone and continuously discharging resulting vaporsfrom the upper portion thereof subsequently returning at least a portionof a resulting distillate to the fractionating zone, and continuouslydischarging a resulting unvaporized heavy hydrocarbon stream withsubdivided particles in a slurry stream from the lower portion of theash zone.

In a broad aspect, the present process is not limited to the use of anyparticular type of subdivided material as the heat carrying medium foreffecting the conversion and coking within the coking zone of the unit,as well as the heating and flashing operation within the confined ashzone for contacting the fractionating bottoms. Catalytic or relativelyinert material may be used to advantage, however, in a preferredoperation, iinely divided coke particles are continuously transferredfrom one zone to the other and are contacted in each of the coking andburning zones in a fiuidized contacting operation. The use of nelydivided coke permits iiuidized transfer and contacting whereby aneiiicient conversion operation may be effected, and in addition is amaterial which is not adversely effected by a burning and heatingoperation. Also, col-re persubdivided coke material within a flash zoneto contact the fractionating bottoms, whereby to supply heat to thatzone of the unit and to aid in an eiiicient overall conversion operationfor effecting a high yield of desired lower boilingA components. The hotstream of coke particles may be withdrawn from the coking zone andpassed to the flashing zone to contact the bottoms stream, oralternately, a hot stream of freshly heated coke particles may be passedfrom the burning zone to the flashing zone. preferred embodiment of theoperation, the hot coke stream passes in a gravity flow to the flashingzone wherein it countercurrently contacts and heats the bottoms streamin order to ash distill it and vaporize the lower boiling componentswhich may be recycled to the fractionating zone. The descending gravityiiow to the flashing zone, permits the introduction of the particles ina relatively compact dense phase stream and precludes the necessity of aiiuidizing medium which in turn would add to the gas and vapor loadeffected within the flashing zone.

The liquid bottoms and coke particles which are withdrawn from the lowerportion of the flashing zone in a slurry stream, may as hereinbeforenoted be utilized to advantage as a fuel for furnace burners and thelike, however, preferably at least a portion of the slurry stream isrecycled to the conversion and coking chamber in order to return thecoke particles to the system and permit further cnversion and cokedeposition. The recycle stream may be returned directly to the cokingchamber or alternately it may be commingled with the residualhydrocarbon charge stream which is being introduced to the coking unit.

Additional advantages and features of the present improved coking andfractionating process of this invention will be more apparent uponreference to the accompanying drawing and to the following descriptionthereof.

Referring now to the drawing, there is shown an elevational diagrammaticview of one embodiment of the improved conversion and coking processwith a fractionation section utilizing a Also, in a 4 hot stream ofsubdivided coke-particles to aid in the fractionating and recoveryoperation. A heavy petroleum charge stock, such as topped or reducedcrude, bunker C fuel, or the like, is introduced to the present unit byway of line I, having control valve 2, and the large riser line orconduit 3 to an elevated coking chamber 4. In this embodiment, thecharge stream is commingled with hot subdivided coke, or other inertparticles if desired, which are introduced into the lower end of riserline 3 by way of standpipe 5 and control valve 6. Hot coke particles arecontinuously withdrawn through the line 5 after having been subjected toburning and heating within the coke burning chamber l. The cokeparticles are heated to a temperature of the order of 1000" F. or morein order to provide a contacting temperature in the riser line and thecoking chamber 4 which is of the order of 850 F. to 1000 F. or more, andthus eiect a desired high temperature conversion and coke deposit on thesubdivided particles. Although not shown in the drawing, preferably theoil charge stream being introduced through line I is preheated to arelatively high temperature of the order of 700 F. to 850 F. whereby theheavy charge stream is in general non viscous and will, upon contactingthe hot subdivided material, deposit a thin film which is coked thereon,and will preclude the adhesion or agglomeration of particles during thecontacting effected in coking chamber 4, or upon passage to the cokeburning and heating chamber l.

Within the coking chamber 4, the resulting thermal distillation andcracked products are passed from the upper portion of the chamberthrough a suitable particle separating apparatus 8 and then transferredthrough a suitable conduit or line 9, having control valve III, to afractionating chamber I I. Entrained coked particles are returned fromthe lower portion of the separator 8 to the contact bed in the lowerportion of the chamber, from which contacted and coked particles arecontinuously withdrawn by way-of a conduit I2 and stripping zone I3. Thelatter chamber has steam or other stripping medium introduced throughline I4 and valve I5 to effect the continuous removal or stripping ofhydrocabron vapors which may be occluded with or entrained with thewithdrawn stream of particles. Stripped particles are continuouslypassed from the lower end of the chamber I5 by way of the line I6 andcontrol valve I'I, and introduced into the coke burning and heatingchamber 'I Where, as indicated in the drawing, the particles arecontinuously fed to the upper portion of the iluidized bed of particlesmaintained in the lower portion of that chamber.

An air or oxygen containing stream is continuously introduced into thelower portion of the chamber I by way of line I 8 and valve I 9, wherebya fluidized contacting of the coked particles may be effected to burn aportion of the coke deposit on the subdivided particles. The oxygencontent' of the fluidizing stream to the burning chamber is, of course,closely regulated to effect only the burning of such coke deposition asis required to heat the fiuidized descending bed of particles to adesired temperature required for commingling with the oil charge and inYturn effect the desired conversion and coking within riser line 3 andchamber B. Hot flue gases are continuously passed from the upper portionof the chamber 'I through a suitable particle separator 20 and outletline 2l having control valve 22, with recovered finely divided particlesbeing continuously returnedtathe; fiuidizedlbedin thelcwer portion ofthe chamber. While. not indicated in' thedraw.- ing, the' hot flue.gaseszbeing: discharged through conduitf2i|- may normally be used to`advantage forthe. generation of high temperatureKV steam or for otherdesiredv heating purposes;

AsLhereinbefore noted,. the heated subdivided coke particles arecontinuously withdrawn in a desired quantity and at. a propertemperature through conduit 5 in order'to subsequently comminglewith thecharge stream. Also, for effectingr a uidized. embodiment of therpresent con- Version-system, the coke particles are preferablymaintained ina' relatively finely divided state so that an effectivetransfer in a. iluidized manner may be made. to the. elevated' cokingchamber. Thus, it may be economically desirable to. place crushing;means or apparatus in the withdrawal line from the coke burningl andheating chamber to. size excessively large particles of. coke and permitthe fluidized operation. An excess quantity of coke may also be removedfrom the unit as necessary; the withdrawal lineA 23 having control valveZ4, is indicated as connecting with the outlet line 5 and providingmeans for withdrawing coke fromV the unit.

The fractionation section of the present embodiment is' showndiagrammatically, with the fractionator Il having an overhead line 25with control valve 2S Which is suitable to dischargeuncondensed'vaporous products from the upper portion of tbefractionator. An outlet line 2l and control valve 28 provides forwithdrawing alight side cut stream, and still another outletl line 29and valve 3! provide means for withdrawingv a heavier side cut-streamwhich mayr beused to advantage as a recycle stream, or alternately aportion thereof utilized as reflux to the column. An inlet line at'- theupper portion of' the vessel Il, indicated as conduit 3 I'with' controlvalve 32, provides means for charging` a suitablereflux stream tothe'top ofthe fractionating column Ill.

1n accordance with the present invention, the unvaporized heavy bottomsfromthe fractionator Il is withdrawn by way of line 33 and valve 34 andintroduced into a suitable confined flash chamber 35, wherein thebottoms stream is subjected tofcontact with a hot subdivided solidparticle stream. In this embodiment, hot contacted coked particles arecontinuously withdrawn from the coking chamber :l through line 36 andvalve 31 and passed to the flash chamber 35. The hot particles areintroduced into the flash chamber at an intermediate pointV in order todescend and countercurrently contact the bottoms stream Y beingintroduced at the lower end of the chamber by way of line 33. It is anadvantageous arrangement and flow to provide means for passing the hotparticles to the flash chamberv in a descending gravity ow, in order topreclude the necessity of utilizing a gaseous transporting medium totransfer the particles to the flash chamber. It is also desirable tomaintain the countercurrent contact between the particles and the bottomstream, as indicated in the drawing, to provide the most efficientheating and distillation of the heavy bottom stream, Resulting vaporsfrom the contact are continuously discharged from the upper portion ofthe hash chamber 35 by way of. linev 33, valve 39, and past a'suitablecondenser or cooler. 40. Resulting condensate is discharged from thecooler by way of line 4i, and at least a portion of the condensatereturned to the fractionator Il through line-'42. having control valvet3. All of. the condensate maybe returned; toV the fractionatorras' aredux: stream. for thelower portion ofthecol.- umn, cir-ifv desired; avportion of the condensate may be withdrawnv and' passed as a refluxstream to. thel top of the column., such: as is introduced throughl line3l. rEhe valve 43. in line 42 and valve 4din line 4l provide means foradjusting or regulating: the quantity of flow to the desired points ofuse.

The unvaporized bottoms in the flash chamber 35 mix with the descendingcoke particles ina slurry stream and may be continuously withdrawnthrough line having control valve. 46. Preferably, at least a portion ofthe slurry stream is passed by way oi line 4l having valve 48, to thecharge line I or riser line 3 to commingle with. the freshly heatedsubdivided particles, whereby to provide a recycle stream which will besubject to further conversion and coking upon contact with the hotparticles within thev riser line and within the coking chamber 4. Aportion of the slurry bottoms may be used to advantage to supply burnersfor furnaces or the like with a suitable fuel. Also, Where desirable,all of the slurry stream may be passed to the coking chamber as arecycle stream to further increase the desired yields or" lower boilinghydrocarbon products and coke.

While the embodiment of the present drawing shows hot coke particlesbeing withdrawn directly from the ccking chamber 4 and passed to theflash chamber 35 to contact the bottom stream of the fractionator, it isto be understood that within the scope of the present invention, heatedsubdivided particles may be withdrawn from the coking unit from a pointother than the c'oking chamber 4. For example, where a highertempera-ture stream of particles is desired, or alternately Where it ispreferable to use a' smaller quantity of particles, a heated particlestream may be withdrawn from. the lower portion of the coke burning andheating chamber "l and continuously transferred by Way of line 49 andvalve 50 to the flash chamber 35 to effect the desired heating andYcontacting of the bottoms stream from the fractionator H, whereby toeect the further high temperature flashing and distillation of thebottoms, as well as add heat and re'- ux to the fractionator Il.Further, it is to be understood that the arrangement of zones indicatedin the drawing is not limiting, the fluidized contacting Zones of thecoking and heating portion of the unit may be superimposed over oneanother or otherwise arranged, while the fractionating and flash heatingzones: need'. not be arranged in the present side to side arrangement asindicated.

I claimas my invention:

1. In a. process for the thermal conversion. of a. heavy hydrocarbon.charge. stream to provide more desirable components, wherein said chargestream continuously contacts subdivided heat carrying particles` in acoking and conversion zone, resulting hydrocarbon vapors are withdrawnand passed to a fractionating zone while said subdivided particles witha coke deposition are passed to a heating and burning zone, the cokedparticles being contacted therein with a regulated stream containingfree oxygen and at least a portion of the coke deposition burned toprovide the .heating ofthe particles therein, with resulting ue gasesbeing discharged from the upper portion of the burning and heating zonewhile at least a portion of the resulting heated. 'subdividedparticles.` are returned. tol1 the coking `and passing the resultingunvaporized bottoms from the lower portion of said fractionating zone toa separate confined flash zone, withdrawing a stream of hot subdividedparticles from at least one of the aforesaid particle contacting zonesand continuously passing said particles to said ash zone, partiallyvaporizing said bottoms stream in theV latter zone and continuouslydischarging resulting vapors therefrom, condensing the vaporsindependently of the vapors from said coking and conversion zone andsubsequently passing at least a portion of the resulting condensate tosaid fractionating zone, and continuously discharging resultingunvaporized heavy hydrocarbons and cooled subdivided particles in aslurry stream from the lower portion of said flash zone.

2. The process of claim l further characterized in that-at least aportion of said slurry stream from said flash zone is passed to saidcoking zone as a recycle stream.

3. The process of claim 2 further characterized in that said slurrystream is commingled with said heavy hydrocarbon charge stream prior tobeing passed to said coking and conversion zone.

4. In a process for the conversion of a heal/5r residual hydrocarboncharge stream to provide more desirable lighter fractions and coke,wherein said charge stream commingles with heated subdivided particles,a iiuidized contacting between the charge stream and said particles iseffected in a confined coking and conversion zone,

resulting hydrocarbon conversion products are withdrawn from the upperportion of the conversion zone and passed to a fractionating zone, atleast a major portion of the contacted subdivided particles are passedwith coke deposition to a burning and heating zone wherein saidparticles are fluidized and contacted by an oxygen containing streamwhereby to burn at least a portion of the coke deposition and effect theheating of the bed of subdivided particles therein, resulting flue gasesare discharged from the upper portion of the burning and heating zone,and at least the major portion of the resulting heated subdividedparticles are passed to said conversion zone, the improvement whichcomprises, fractionating the hydrocarbon vapors withdrawn from saidconversion zone within said fractionating zone, withdrawing desiredhydrocarbon' fractions therefrom and continuously passing unvaporizedbottoms from said fractionating zone to a confined flash zone,withdrawing a continuous stream of heated subdivided particles from atleast one of the aforesaid fiuidized contacting zones andcountercurrently contacting and partially vaporizing said bottoms streamwithin said flash zone, condensing the resulting vapors independently ofthe vapors from said coking and conversion zone and passing at least aportion of the resulting condensate to said fractionating zone as areflux stream, continuously discharging the resulting unvaporizedbottoms from the lower portion of said flash zone in a slurry streamwith the subdivided coke particles charged thereto and passing atleast aportion of said slurry stream to said coking and conversion zone as arecycle stream.

5. The process of claim 4. still further characterized in that the hotsubdivided particles passed to said flash zone are continuouslywithdrawn from said coking and conversion zone.

6. The process of claim 4 further characterized in that said hot streamof subdivided particles passing to said flash zone are withdrawn fromsaid heating and burning zone.

'7. A process for the conversion of -a heavy residual hydrocarbon chargestream to provide more desirable lower boiling fractions and coke whichcomprises, passing said charge stream to a conned coking chamber withheated subdivided coke particles and effecting a uidized contactingtherein, withdrawing resulting hydrocarbon conversion products from theupper portion of the conversion zone and passingrthem to a fractionatingzone, passing at least a major portion of the contacted subdividedparticles with coke deposition to a burning and heating zone whereinsaid particles are contacted by an oxygen containing stream and at leasta portion of the coke deposition burned to effect the heating of the bedof particles therein, discharging resulting ilue gases from the upperportion of the burning and heating zone and passing at least a majorportion of the resulting heated subdivided particles to said conversionzone, fractionating the hydrocarbon vapors withdrawn from said cokingand conversion zonne within said fractionating zone, withdrawing desiredhydrocarbon fractions therefrom and continuously passing unvaporizedbottoms from said fractionating zone to a confined flash zone, passing acontinuous stream of hot subdivided coke particles from said coking zonein a compact stream to an intermediate portion of said flashing zone,countercurrently contacting and partially vaporizing said bottoms streamtherein, condensing the vapors from said flash zone independently of thevapors from said coking zone and passing at least a portion of theresulting condensate to said fractionating zone as a reflux stream,continuously discharging the resulting unvaporized bottoms together withcoke particles from the lower portion of said flashing zone in a slurrystream, and recycling at least a portion of said slurry stream to saidcoking and conversion zone, with the slurry stream commingled with saidheavy residual charge stream prior to contacting said freshly heatedsubdivided particles from said coke burning and heating zone.

8. A process for the conversion of a heavy hydrocarbon oil whichcomprises reducing the oil to coke in a coking zone by contact thereinwith inert solid heat-carrying particles, thereby depositing coke onsaid particles. fractionating the resultant vapors to separate therefromlow boiling products and a heavier liquid bottoms fraction, removingseparate streams of solid particles from said coking zone; introducingone of said streams to a combustion zone and therein burning cokedeposit from the particles, returning resultant hot particles to thecoking zone, introducing another of said streams and said liquid bottomsfraction to a flash zone and therein partially vaporizing said fractionby contact with the particles of said other stream, and removing fromthe lower portion of the flash zone a slurry of ooked particles and theun- ''aporized liquid portion of said bottoms fracion.

9. The process of claim 8 further characterized that the vapors fromsaid flash zone are con- 9 densed independently of the vapors from saidcoking zone and at least a. portion of the resultant condensate utilizedas a refluxing medum during the fractionation of the vapors from thecoking zone.

10. The process of claim 8 further characterized in that said inertparticles consist essentially of coke.

WILLIAM K. HUNTER.

REFERENCES CITED The following references are of record in the file ofthis patent:

Number 10 UNITED STATES PATENTS Name Date Kuhl Jan. 25, 1944 HemmingerSept. 19, 1944 Hemminger Nov. 7, 1944 Arveson Dec. 17, 1946 Keith July20, 1948 Hemminger et al. Aug. 24, 1948 Bonnell Feb. 15, 1949

1. IN A PROCESS FOR THE THERMAL CONVERSION OF A HEAVY HYROCARBON CHARGESTREAM TO PROVIDE MORE DESIRABLE COMPONENTS, WHEREIN SAID CHARGE STREAMCONTINUOUSLY CONTACTS SUBDIVIDED HEAT CARRYING PARTICLES IN A COKING ANDCONVERSION ZONE, RESULTING HYDROCARBON VAPORS ARE WITHDRAWN AND PASSEDTO A FRACTIONATING ZONE WHILE SAID SUBDIVIDED PARTICLES WITH A COKEDEPOSITION ARE PASSED TO A HEATING AND BURNING ZONE, THE COKED PARTICLESBEING CONTACTED THEREIN WITH A REGULATED STREAM CONTAINING FREE OXYGENAND AT LEAST A PORTION OF THE COKE DEPOSITION BURNED TO PROVIDE THEHEATING OF THE PARTICLES THEREIN, WITH RESULTING FLUE GASES BEINGDISCHARGED FROM THE UPPER PORTION OF THE BURNING AND HEATING ZONE WHILEAT LEAST A PORTION OF THE RESULTING HEATED SUBDIVIDED PARTICLES ARERETURNED TO THE COKING ZONE TO SUPPLY HEAT FOR EFFECTING THE AFORESAIDCONVERSION AND COKING OF THE HEAVY HYDROCARBON CHARGE STREAM, THEIMPROVEMENT WHICH COMPRISES, FRACTIONALLY SEPARATING THE HYDROCARBONVAPORS PASSING FROM SAID COKING AND CONVERSION ZONE WITHIN SAIDFRACTIONATING ZONE, WITHDRAWING DESIRED HYDROCARBON FRACTIONS FROM SAIDZONE AND PASSING THE RESULTING UNVAPORIZED BOTTOMS FROM THE LOWERPORTION OF SAID FRACTIONATING ZONE TO A SEPARATE CONFINED FLASH ZONE,WITHDRAWING A STREAM OF HOT SUBDIVIDED PARTICLES FROM AT LEAST ONE OFTHE AFORESAID PARTICLE CONTACTING ZONES AND CONTINUOUSLY PASSING SAIDPARTICLES TO SAID FLASH ZONE, PARTIALLY VAPORIZING SAID BOTTOMS STREAMIN THE LATTER ZONE AND CONTINUOUSLY DISCHARGING RESULTING VAPORSTHEREFROM, CONDENSING THE VAPORS INDEPENDENTLY OF THE VAPORS FROM SAIDCOKING AND CONVERSION ZONE AND SUBSEQUENTLY PASSING AT LEAST A PORTIONOF THE RESULTING CONDENSATE TO SAID FRACTIONATING ZONE, AND CONTINUOUSLYDISCHARGING RESULTING UNVAPORIZED HEAVY HYROCARBONS AND COOLEDSUBDIVIDED PARTICLES IN A SLURRY STREAM FROM THE LOWER PORTION OF SAIDFLASH ZONE.